The present invention relates generally to a Zero-Turning-Radius (“ZTR”) vehicle. Specifically, the present invention restricts movement of the front wheels as desired by a user of the vehicle.
Whether a lawn mower is utilized commercially or for personal use, efficient operation is essential. Typically, contractors desire to mow a yard as quickly as possible so they may complete more jobs in a day. Similarly, a homeowner wants to mow his yard quickly so that he may move on to other activities. ZTR vehicles are particularly useful in the lawn care industry. ZTR vehicles adapted to include various lawn care attachments have become particularly popular in the lawn care industry because their tight cornering capability obviates the constant need to shift gears from forward to reverse or to drive in a wide loop in order to turn around, as is necessitated by the large turning radius of a non-ZTR vehicle. These benefits of a ZTR vehicle can save time for the operators.
ZTR vehicles have the capability to make turns having a center of rotation at the midpoint between the independent rear drive wheels. This is accomplished by driving the independent rear drive wheels at different speeds, and even in different directions, with respect to each other. Operators of ZTR vehicles steer the vehicle by maneuvering separate levers responsible for controlling the independent drives of each rear wheel rather than providing a steering wheel. Often the operators find the dual lever system extremely difficult to operate.
In ZTR vehicles, since the independent rear drive wheels steer the vehicle as well as engage the ground, it is not necessary for the front wheels to be steerable. Therefore, caster wheels are often used for the front ground-engaging wheels. Caster wheels spin 360 degrees about a vertical axis of rotation but are not steered. Rather, the front caster wheels simply respond to the movement and direction of the vehicle as dictated by the rear drive wheels.
One problem associated with the front caster wheels results as the ZTR vehicle is driven up or down hill and any variation in the speed and direction between the independent rear drive wheels causes one or both of the front caster wheels to pivot. As either or both of the front caster wheels pivot, the ZTR vehicle tends to turn away from the intended path of travel. Moreover, the ZTR vehicle typically has a heavy load over the front caster wheels which results in a large moment over the rear wheels. This large moment over the rear wheels also causes the ZTR vehicle to turn away from the intended path of travel. To counteract this unintended movement of the ZTR vehicle, the operator must adjust the speeds and/or directions of the rear drive wheels to steer the ZTR vehicle back to the intended path of travel. As can be appreciated, the constant adjustment to the rear drive wheels can be difficult to learn.
Another problem with these non-steerable front wheels results when a ZTR vehicle is driven laterally across the side of a hill. As the ZTR vehicle is driven across the hill, the gravitational force of the ZTR vehicle tends to pull the vehicle down the hill, and correspondingly the front caster wheels turn towards the bottom of the hill. Again, to maintain the intended path of travel, the operator must continually adjust the direction and speed of the independent rear drive wheels.
The need exists for a ZTR vehicle that can selectively limit pivotal movement of the front wheels of the vehicle separate from the rear drive wheels in order to provide more efficient and effective operation and reduce or eliminate the unintentional veering of the ZTR vehicle. The need also exists for a ZTR vehicle that is more user-friendly.
Thus, there is a need for improvement in this field.